Sound recording apparatus



Aug, 10, 1937. KLEBER 2,089,484

SOUND RECORDING APPARATUS Filed Nov. 28, 1933 2 Sheets-Sheet 2 nvwszvron. lac/(501v O M55512,

WA A TTORNE Patented Aug. 10, 1937 UNITED STATES PATENT OFFICE 24 Claims.

This invention relates to the photographic recording of sound and associated records on films. More particularly the invention relates to apparatus for makinga variable width sound record on a movable film, wherein the image of an illuminated slit or line source of light is produced on the film transversely of the direction of movement of the film, and in which the image of the slit or source of light is varied in length by a mechanicallyoscillatable controller to define the profile ofthe sound track on the film.

This application is a continuation in part of my application Serial Number 391,201 filed September 9, 1929, and issued as Patent No. 1,937,089,

Nov. 28, 1933, for a Machine for recording and reproducing sound motion pictures.

An object of the present invention is to provide improved and simplified apparatus for producing sound records of the kind referred to.

Another object is more effectively to control the opening through the illuminated slit or to control the area of the image on the film in response to a given displacement of the mechanical controller which defines the profile oi the sound track on the film.

Another object is to increase the frequency range of sounds eiIectively recorded on the film.

Another object is to improve the operation of the oscillatable controllers for varying the profile p0 of the sound track by rendering the controllers properly aperiodic in their movements.

Other objects are to increase the amplitude of variations in width of the sound track for a given intensity of sound, to improve the quality of the 35 record, and to produce a sound record of such form as to reduce disturbing noises which tend to be reproduced when the film is passed through a sound reproducer.

In accordance with one modification of the 4 present invention, apparatus is provided for making a variable width sound record on a movable photographically sensitive film. A source of light transmits a beam to the film through a slit in a screen, producing an image of the slit on the 45 film transversely of the direction of movement of the film. A plurality of controllers, such as sound controlled oscillatable shutters or mirrors, are provided to act on different parts of the image of the slit on the film, one controller varying the 50 position of one terminus of the line image of the slit and another controller varying the position of another terminus of the line image.

One form of oscillatable shutter has an edge thereof inclined across and arranged to variably 55 intercept the path of light through one end of the slit. Another shutter operating in conjunc tion with the first shutter is inclined across and arranged to variably intercept the path of light through the other end of the slit independently of the first shutter. By arranging the shutters so that one is selectively operable at a higher natural frequency of oscillation than the other shutter, a more faithful record of the sound may be obtained and sound waves having a wider range of frequencies may be recorded on the film. Another application of the two-shutter or twocontroller apparatus reduces disturbing :ioises by reducing the area of the opaque part of the negative film, thus reducing the area of the transparent part of the final positive film during intervals when the sound amplitude or the amplitude of the controller is small or negligible. In this case one shutter or controller produces the sound record, while the other shutter is controlled by a detector operated under sound con-- trol in an arrangement for producing a quick response of the shutter for increases of amplitude and for producing a retarded operation of the shutter in response to a decrease of sound amplitude. In other forms of apparatus illustrative of the present invention, mirrors are employed to accomplish these results.

In a modified form of the invention, two separate shutters define the same end of the line oi. light to be produced on the film. Each shutter has an edge inclined across the line source of light, the two edges being inclined oppositely with respect to the line. The shutters are arranged to oscillate in unison and to maintain the point of intersection of their inclined edges directly over the longitudinal center line of the slit or line of light. This arrangement avoids a certain amount of distortion of the sound incident to the use of a single inclined shutter.

Fig. 3 shows a modification of a part of the apparatus of Fig. 1.

Figs. 4 and 5 show fragments of films produced by the apparatus of Figs. 1 and 3.

Fig. 6 shows a modification of the shutter controlling apparatus of Figs. 1 and 3.

Fig. 7 is a modification of Fig. 1 adapted to reduce undesired noise which may be reproduced by transparent portions of the film.

Fig. 8 shows a fragment of the negative film produced by the apparatus of Fig. '1.

Fig. 9 shows a fragment of the positive film copied from the negative shown in Fig. 8.

' Fig. 10 is a diagram showing difierent places in the optical system where the apparatus described her in may be introduced.

Fig. 11 s..ows a modified form of light deflecting apparatus.

Fig. 12 shows amodification of the apparatus of Fig. 11.

Fig. 13 is a diagram of an oscillation damping device.

Figs. 14 and 15 show modified forms of shutters.

In Fig. 1 the lamp I, or other suitable concentrated source of light, projects a beam of light to the photographically sensitive film 2, which is guided and positioned by rollers 3 over which the film feeds. An optical system, comprising the condenser lenses 4 and the objective lenses 5 may be either of spherical or cylindrical form. A screen 8 intercepting the light beam from source I to film 2 has a slit 1 therein positioned with respect to the optical system 4, 5, so that light from condenser 4 is concentrated on the slit, and an image of the slit or line source of light is projected on the film at 8 transversely of the direction of movement of the film. A shutter 9 having an edge I0 which is inclined across one end of slit 1 is pivoted at H, so that it may oscillate uncier the control of armature l2 attached to the shutter transversely of the slit. Another shutter I3 has an edge ll inclined across the other end of slit I. Shutter I2 is oscillated around pivot 19 by means of armature i6. Shutters 9 and I3 variably intercept the path of light through the respective ends of slit 1 which they overlap and thus vary the position of the two edges of the light beam corresponding respectively with the two edges of the sound track. Sound waves impressed upon microphone I! or other suitable pick-up devices produce sound controlled currents which are increased in amplitude by amplifier l8.

Output circuit I 9 of the amplifier has low pas filter 20 and high-pass filter 2| connected therein. Electromagnet 22 controls armature l2 and is connected with filter 20. Currents of a frequency below a value pre-determined by the upper cut-off frequency of filter 20 selectively energize magnet 22, while electromagnet 23, controlling armature I6, is selectively energized only by currents above said pre-determined frequency, determined by the low cut-off frequency of filter 2|.

In operating the apparatus of Fig. 1, speech or other sound waves actuating transmitter l1 produce electric currents, the low frequency components of which actuate shutter 9 and the high frequency components of which actuate shutter l2, so that the position of one terminus of the line representing the image of the slit on the film is varied at a lowfrequency by shutter 9 and the position of the other terminus of the line image is varied at a high frequency by shutter I3, while the film is fed transversely to the line image, thereby producing a record as shown in Fig. 2. The end of the line varied at a low frequency, traces the low frequency profile-24, while the end of the line varied at a high frequency traces the profile' 25. The two profiles or edges of the sound track are thus varied in accordance respectively with two currents of different character, one a low frequency current and the other a high frequency current.

Fig. 3 shows more fully than Fig. 1, the arrangement for supporting the shutters and maintaining them in a normal position about which the shutters oscillate. To accomplish this purpose each armature I2, I 6, is supported at one end of a spring 28, the other end of each spring being fastened to a fixed support 21. Spring 26 yields in response to the oscillations of the shutter and restores the shutter to its normal position. S utter 28 is of larger dimensions or has a larger mass than shutter 29, Fig. 3, or may be provided with a lighter spring 26 than the spring for shutter 29, so that shutter 29 has a higher natural frequency of oscillation than shutter 26. and is thus selectively operable at a higher frequency than shutter 28.

By suitably. mechanically tuning shutters 28 and 29, the electrical selectivity obtained by filters 20 and 2| may not be necessary where extreme selectivity is not desired and the filters may be removed from the circuit by transferring switches 30 and 3| to their upper positions, thus eliminating the filters from the circuit. It will be understood that filters 20 and 21 may similarly be omitted in Fig. l, in which case shutters 9 and i3 vibrate at the same frequency and produce a record as shown in Fig. 5, wherein the profile 33, at one side of the sound track is similar to the other profile 34 at the other side of the track.

If one of the shutters l3, in Fig. l, or 29, in Fig: 3, be made non-responsive to current, as by opening the control circuit therefor, or leaving it de-energized, only one of the shutters operates to produce a variable profile 32, as shown in Fig. 4. It will be understood that magnets 22 and 23 may be connected to independent circuits instead of to a common circuit l9, and may thus be employed to produce two independent profiles on a single sound track of the type shown in Fig. 5. One of these profiles may represent a complete sound record, while the other profile of the same track may be utilized to control the operation of the apparatus for reproducing the sound recorded on the film, as, for example, the volume of the sound or some other characteristic or operation which it is desired to control in connection with the reproduction of the sound.

In Fig. 6, the armatures 36 and 31, controlling shutters 38 and 39, are both operated by electromagnet 40, which is controlled by the sound controlled currents representing the sound which is to be recorded. In this form of apparatus the single magnet 40 takes the place of magnets 22 and 23, Figs. 1 and 3. When shutter 38 is to have a difierent frequency response from shutter 39, as in the case of the shutters of Figs. 1 and 3, mechanical tuning of shutters 28 and 39 may be provided.

In order to reduce disturbing noises which tend to be reproduced when the film is passed through the sound reproducer, it has been found desirable to reduce the area of the transparent portions of the film which are to be exposed to light in the reproducing machine, as shown in Fig. 9 by the positive film having the opaque area defined by profile 49. closely following the amplitude or intensity variations of the sound current represented by profile 48.

Fig. 7 provides apparatus for producing a sound record in which disturbing noises of the kind referred to are reduced. Sounds impressed upon the microphone or pick-up device 49 produce currents amplified in amplifier 4i, the amplified currents being transmitted through filter 42 to shutter magnet 22. Filter 42 is designed to limit the frequency of response of magnet 22 to a range 5 which it is desired to record on the film, but may be omitted from the circuit, if desired. A part of the amplified current from amplifier 41 is transmitted to detector 43, connected with the same circuit supplying current to magnet 22, and having its output circuit connected through filter 44 with shutter magnet 23. Detector 43 may be any suitable form of detector or rectifier. Low pass filter 44, in conjunction with detector 43 and magnet 23, limits the frequency response of the magnet to frequencies below the audible range,v so that magnet 23 can not produce an audible sound record, but produces a low frequency profile which follows closely the amplitude or intensity variations of the sound current. The combination of detector 43, filter 44 and magnet 23, is such that it is possible to retard the deenergization of magnet 23 as compared with the time required for energization thereof by the detected current. One method of accomplishing 25 this result is to adjust low pass filter 44 to introduce the desired delay characteristic.

Fig. 8 shows a sound track producedllas a photographic negative by the apparatus of Fig. 7. Profile 45 represents a record of the sound, while the lower frequency profile 48, produced by rectified sound current passing through magnet 23,

follows closely the points of maximum amplitude of profile 45, but since the response of magnet 23 is limited to frequencies below the audible range,

profile 46 does not show the audible frequency variations seen in profile 45. It will also be noted that profile 46 at point 41 is spaced somewhat further from profile 45 than at the point marlred 46, thereby showing a more rapid energization of magnet 23 and a retarded de-energization of the magnet as the image of the light source projectcd on the film moves along the film in a downward direction in Fig. 8.

Fig. 9 shows a positive print made from Fig. 8.

The transparent area between profiles 48 and 43 will be seen to have a much smaller extent than if the opaque area defined by profile 49 had been omitted. This form of record, having a reduced area of transparency. has a correspondingly small 50 tendency to produce undesirable noises from irregularities in the transparent area of the film.

Fig. 10 shows the source of light i, transmitting light through condenser 4, slit 50, objective 5-, focus 5|, objective 52 to focus 53 on film 2.

The shutter arrangement shown in Figs. 1. 3 or 6 may be substituted in Fig. 10 directly at slit 50, or with slit 50 in the position shown, the shutters may both be located at point Si or at point 53. in the path of light forming the image 53 on so film 2; or if desired one shutter of an associated pair, such as 9, l3, Fig. 1, may be located at one of the points 50, 5|, or 53, and the other shutter of the pair located at any other of these points. It will also be understood that the lamp source I 65 may be placed sufficiently close to slit 50 to take the place of the combination of source I with condenser 4. Also, slit 50 may be moved to point Si or 53.

It will be noted that when the source I is placed sufilciently close to slit 50 to avoid the use of condenser lenses 4, and when the slit 50 together with the shutters are placed at point 53, as referred to above, lenses 5 and 52 are obviously unnecessary, and the resulting combination is of 75 extremely simple construction. In most cases,

however, the arrangement'of the slit and shutters ture 63 in turn is similar to armatures l2 and I3,

Fig. 3, and is vibrated by electromagnet Bl, energized by sound controlled currents. Mirrors and}! are so adjusted that they are substantially parallel in their normal, undefiected position. The source of,light I, transmits light through the condenser lenses 4, then through slit 1 in opaque screen 6, then through objective lenses 5 to mirrors 80. Bi, from which the light is reflected to film 2, to produce an image thereon of the line of light defined by slit 1. Displacement of armature 68 causes the mirrors to depart from parallelism, thereby producing a double profile on the sound track on film 2, as shown in Fig. 5.

If desired, the mirrors may be operated by independent magnets 22, 23, as shown in Fig. 12. These magnets may be responsive. respectively, to different frequencies, as described in connection with Fig. 1. Magnet 22 may have a natural resonance characteristicof low frequency and magnet 23, a natural resonance characteristic of higher frequency. Magnet 22 vibrates armature l2, thereby oscillating mirror 60 at low frequency, while magnet 23 vibrates armature l6, thereby oscillating mirror 6| at a high frequency. The operation of armatures l2 and i6 is at the frequencies described in connection with Fig. 1. and it will be understood that the use of filters for selecting these frequencies, as shown in Fig. 1, or the use of other suitable frequency selecting means for this purpose, comes within the scope of the present invention. The record produced by mirrors 80, 6|, in Fig. 12 is of the type shown in Fig. 2, as described in connection with Fig. 1. i If desired, magnets 22 and 23 may be responsive to the same range of frequencies to produce independent records on the same sound track as shown in Fig. 5.

In some cases it is desirable that the mirrors or other controllers be properly damped so as to be rendered substantially aperiodic in their movement throughout the range of frequencies impressed thereon. For thispurpose it is advisable to apply the damper directly to the vibrating element, for example, the mirror, on account of the likelihood of independent vibration of the individual parts of the moving system. In doing this, care must be taken not to introduce so much damping as to prevent sufficient free movement of the mirror or controller; however, the damping should be suflicient to prevent distortion due to pronounced resonance of the parts.

In overcoming these difiiculties it has been found that a mirror of small size may have its oscillations damped by a clamping device such as is shown in Fig. 13, wherein the mirror 54 having a hinge support 55 at one edge thereof, and armature 56 connected therewith, is provided with the damping element 5'! under another edge of mirror 54 remote from the hinge 65. The damper 51 may be of any suitable material having a texture which is not too hard. smerubberhasbeenfoundtobeverysatisiactory ior this purpose. It will be understand that a piece oi sponge rubber similar to theelemeat 51, Fig. 18, may be employed to damp the oscillation oi any oi the controllers described 5 herein. For erample, a piece oi sponge rubber may be inserted between the magnet and its associated armature in any oi the controller units described herein.

The iorm oi shutter 65' shown in Fig. 14 is n similar to the shutters oi Figs. 1 and 3, having the inclined edge in cooperating with slit 1 and oscillatable around pivot ll. Shutter ll, however, has an arm 86 terminating in a spring extension 81 secured to iulcrum 88. Am 68 is m vibrated by armature l2 operated by magnet 22. Fig. 15 shows a still iurther iorm oi shutter arrangement, having two separately oscillatable shutters I0 and Ii, having pivots l2, 18, about which the respective shutters oscillate. Shutter has an edge 14, and shutter II has an edge It, inclined across the slit and arranged to define the same end oi the line oi light to be iormed by light passing through the slit 1. Edges l4 and are inclined oppositely with respect to the slit or line source oi light I and intersect each other directly over the longitudinal center line oi the slit or line oi light. the shutters being arranged to oscillate in unison transversely oi the line oi light to vary the length oi the line oi light, while maintaining the point oi intersection oi edges H, 15, over said center line. A single magnet 18 separately actuates armature 11 attached to shutter 10 and armature II attached to shutter II. This double iorm oi shutter has the advantage over the single shutter, shown in Figs. 1, 3, 6 and 7, oi symmetrically intercepting the light through slit 1, thereby avoiding a certain amount oi distortion introduced by the use of a single shutter. It will be understood that a double shutter oi the iorm shown in Fig. 15, may be substituted ior each oi the single shutters shown in Figs. 1, 3, 6, and 7. The shutters shown in Figs. 14 and 15 may be utilized in a system such as shown in Fig. 10. Shutter 65 oi Fig. 14 may be inserted at any one oi the points 50, 5| and 53, Fig. 10, to variably intercept the light through one end of the slit 60, and a similar shutter may be placed at any one oi the points 50, Si or 53 to'variably intercept the light through the other end oi slit 50. Slit may alternatively be located at position 5| or 53. In a similar manner the shutter arrangement oi Fig. 15 may be inserted at any one oi the points 50. Si or 53 oi Fig. 10, to control 55 the light through one end oi slit 50, and a similar shutter arrangement inserted, ii desired. to control the light through the other end oi slit 50.

When one oi the light modulators oi Fig. 14

or Fig. 15, is located at each end oi the slit in the position 50, Fig. 10, as reierred to above, it will be seen that the relationship oi the modulators to lenses 4 and 5 and the other elements, is similar to that shown in Fig. 1, and ior most purposes such a location oi the modulators is to be preierred.

In each oi the cases where the line oi light is independently intercepted at its two ends, as in Fig; 1, ior example, a given displacement oi each shutter produces a greater amplitude oi va- 7 riation oi width oi the sound track than is produced by a shutter operating with the same displacement in conjunction with only one end oi the slit.

Various other modifications and changes will be obvious to those skilled in the art as coming within the teachings oi the present disclosure. Further advantages, objects and uses oi the disclosed apparatus will'also be apparent. The invention is not to be limited to the exact structures as shown as illustrations of the invention, but only by the appended claims.

I claim:

1. The method oi making a sound track on a moving sensitive film, which comprises transmitting a beam oi light to the film, and separately varying in accordance with waves of diiierent character, the position oi the two edges of the light beam corresponding respectively with the two edges oi the sound track.

2. The method oi recording sound on a moving sensitive film which comprises producing a line oi light on the film transversely to the direction oi movement oi the film, varying the length oi the line at one end in accordance with a characteristic oi sound, and varying the length of the line at the other end in accordance with another characteristic.

3. In apparatus ior use in recording sound on a moving photographlcally sensitive film, means ior transmitting a beam oi light to the film ior tracing a record track thereon, means ior varying the position of one edge oi the track in accordance with sound wave energy oi certain character, and means ior varying the position oi the other edge oi the track selectively in accordance with wave energy oi different character.

4. In a light controller ior use in conjunction with a line source oi light in recording sound on a moving sensitive film, a vibratable light modulator and means to vibrate the same to vary the length of the line at one end oi the line in accordance with sound controlled current, and another vibratable light modulator and means to vibrate the same to vary the length oi said line at the other end selectively in accordance with a current having a characteristic diiiering from that oi said first mentioned current.

5. In a light controller for use in recording sound on a moving sensitive film, means arranged to define the length oi a line oi light to be produced on the film, said means including means to vary the length of the line at one end in accordance wi'h sound controlled current and means to vary the length oi the line at the other end selectively in accordance with a current having a characteristic diiiering irom that oi said first mentioned current.

6. In apparatus ior use in recording sound on a moving sensitive film. means ior producing a line oi light on the film transversely to the direction oi movement oi the film, means to vary the length oi the line at one end in accordance with sound controlled current, and means to vary the length oi the line at the other end selectively in accordance with a current having a characteristic diiierent-irom that oi said first mentioned current.

7. In apparatus ior use in recording sound on a moving photographically sensitive film, means for transmitting a beam oi light to the film for tracing a record track thereon, means ior varying the position oi one edge oi the track in accordance with sound wave energy oi certain irequency. and means ior varying the position oi the other edge oi the track selectively in accordance with wave energy oi difi'erent irequency.

8. In apparatus ior use in recording sound on a moving sensitive film, means ior defining the length oi a line oi light to be produced on the film transversely to the direction oi movement at the film, said means including means to vary the length of the line at one end in accordance with sound controlled current within a certain frequency range and means to vary the length of the line at the other end selectively in accordance with a current of a different frequency range.

9. The method of making a sound track on a moving sensitive film; which comprises transmitting a beam of light to the film, vibrating an edge of the light beam corresponding with one edge of the sound track selectively in accordance with high frequency components of a sound wave. and vibrating another edge of the light beam corresponding with the other edge of the sound track selectively in accordance with low frequency components of a sound wave.

10. In apparatus for use in recording sound on a moving sensitive film, means for defining the length of a line of light to be produced on the film transversely to the direction of movement of the film, said means including means to vary the length of the line at one end selectively in accordance with high frequency current and means to vary the length of the line at the other end in accordance with low frequency current.

11. In apparatus for use in making a variable width sound record on a moving sensitive film, means for defining the length of a line of light to be produced on the film transversely of the direction of movement of the film, said means including a vibratable light modulator for varying the length of the line at one end of the line and another vibratable light modulator for varying the length of the line at the other end of the line, means including a frequency selective circuit responsive to sound controlled current for vibrating one of said modulators, and means including another frequency selective circuit responsive to current of a different frequency for vibrating the other of said modulators.

12. In apparatus for use in making a variable width sound record on a moving sensitive film, means for defining the length of a line of light to be produced on the film transversely of the direction of movement of the film, said means including a pair of selectively oscillatable light modulators having a pair of adjacent portions. said modulators extending in opposite directions from said adjacent portions, hinged supports for said modulators at points thereon remote from said adjacent portions, said modulators being so arranged that when oscillating, one modulator varies the length of the line of light at one end 55 of the line and the other modulator varies the length of the line of light at the other end of the line, and means whereby said modulators may be vibrated in accordance respectively with sound controlled currents of different character.

13. A light controller for ,use in recording sound on a moving sensitive film, including a screen having a slit therein, a pair of separate shutters inclined across the slit and respectively covering opposite ends of the slit, and means responsive to sound controlled current for vibrating said shutters transversely of the slit in accordance respectively with different characteristics of the sound current.

14. In a light controller for use in conjunction with a line source of light in recording sound on a moving sensitive film, a shutter and means to vibrate the same to vary the length of the line at one end of the line in accordance with sound controlled current, and another shutter and means to vibrate the same to vary the length of said line at the other end selectively in accordance with a current having a characteristic differing from that of said first mentioned current, said shutters being inclined relatively to the line source of light and vibrating transversely to the line.

15. A light controller for use in recording sound on a moving sensitive film, including a screen having a slit therein, a pair of separate shutters inclined across the slit and respectively covering opposite ends of the slit, means responsive to sound controlled current for vibrating said shutters transversely of the slit, and means for causing the vibrations of one of said shutters to be at a lower frequency than that of the other of said shutters.

16. In apparatus for use in making a variable width sound record on a moving sensitive film, means for defining the length of a line of light to be produced on the film transversely of the direction of movement of the film, said means including a shutter having an edge inclined relatively to the line of light and defining one end of the line and another shutter having an edge inclined relatively to the line of light and defining the other end of the line, and means whereby said shutters may be vibrated transversely of the line of light and whereby one of said shutters is responsive to sound current of predetermined frequency and the other of said shutters is selectively responsive to current of a different frequency.

17. In a light controller for use in recording sound on a moving sensitive film, a pair of separately oscillatable mirrors arranged to control the length of a line of light to be produced on the film, and means to oscillate said mirrors to vary the length of the line at both ends in accordance with sound controlled current.

18. In a light controller for use in recordin sound on a moving sensitive film, a pair of oscillatable mirrors arranged to control the length of a line of light to be produced on the film, means to oscillate one of said mirrors in accordance with sound controlled current to vary the length of the line at one end, and means to oscillate the other of said mirrors in accordance with a current having a characteristic difiering from that of said first mentioned current to vary the length of the line at the other end.

19. In apparatus for use in making a variable width sound record on a moving sensitive film, means for defining the length of a line of light to be produced on the film transversely of the direction-of movement of the film. said means including two separately oscillatable mirrors having an edge of-one adjacent an edge of the other, said mirrors extending in opposite directions from their adjacent edges and having hinged supports, said mirrors being so arranged that when oscillating, one mirror varies the length of the line 'of light at one end of the line and the other mirror varies the length of the line of light at the other end of the line, means whereby one of said mirrors may be oscillated in accordance with sound controlled current and whereby the other of said mirrors may be oscillated in accordance with a current having a characteristic differing from that of said first mentioned current.

20. In apparatus for use in making a variable width sound record on a moving sensitive film, means for defining one end of a line of light to be produced on the film, said means including a shutter having an edge inclined relatively to the line of light and another shutter having an edge inclined relatively to the line of light in an opposite sense to that 01 the first mentioned edge, said inclined edges intersecting each other directly over the center line of the line of light and being vibratable in unison transversely oi the line of light while maintaining their point of intersection over said center line, and means responsive to sound controlled current for vibrating said shutters in unison for varying the length of the line of light.

21. A shutter mechanism for use in recording sound on a movable sensitive film, comprising a screen having a slit therein and two separately oscillatable sound controlled shutters, each having an edge inclined across the slit and arranged to control the same end of a line of light to be formed by light passing through the slit, said inclined edges being oppositely inclined with respect to the slit and intersecting each other directly over the longitudinal center line of the slit, and means responsive to sound controlled current for oscillating said shutters in unison, while maintaining the point of intersection of their inclined edges over the center line of the slit.

22. A shutter mechanism for use in recording sound on a movable sensitive film, comprising a screen having a slit therein and two separately oscillatable sound controlled shutters, each having an edge inclined across the slit and arranged to control the same end of a line of light to be formed by light passing through the slit, said inclined edges being oppositely inclined with respect to the slit and intersecting each other directly over the longitudinal center line 01' the slit, and a single magnet responsive to sound controlled current for oscillating said shutters in unison, while maintaining the point of intersection of their inclined edges over the center line of the slit.

23. In apparatus for use in making a variable width sound record on a moving sensitive film. means for defining the length of a line of light to be produced on the film transversely of the direction of movement of the film, said means including a pair of shutters inclined relatively to the line of light and respectively defining opposite ends of the line, means for vibrating one of said shutters transversely of the line oi light in accordance with sound controlled current, and means for vibrating the other 01' add shutters transversely of the line of light in accordance with the intensity of the sound controlled current.

24. In a light controller for use in recording sound on a moving sensitive film, means for defining the length of a line of light to be produced on the film transversely of the direction of movement of the film, said means including a pair of shutters inclined relatively to the line 01 light and respectively defining opposite ends of the line, means for vibrating the first of said shutters transversely to the line of light in accordance with sound controlled current, means for detecting said current. means for vibrating the second of said shutters transversely to the line of light in accordance with a component of the detected current, and means for retarding the deenergization oi said second shutter as compared with the time required for energization thereof by the detected current.

JACKSON 0. KLEBER.

CERTIFICATE OF CORRECTION.

Patent No. 2,089 .484.

August 10, 1937 JACKSON 0. KLEBER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Page 2,

first column, line 35, strike out the words "transversely of the slit"; line 39, after "13" insert the words vibrate transversely of the slit 7 to; and second column, line 7, after of the slit; page 4, second column.

line 61, claim 6, for "different" read differing; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of September, A. D. 1937.

(Seal) Henry Van Arsdale "oscillate"-insert transversely Acting Commissioner of Patents.

D I s c L A l M E R 2,089,484.-Jackson 0. Kleber, Long Island City, N. Y. Sous" Rncoanmo A- rm'ros. Patent dated August 10, 1937. Disclaimer filJlA b the u- :14! PZM be.

pril 11, 1940,

Radio Corporation of America and Electrical Research l 0mm April :0, 1940.] 

